Warren Buffett heard Martin Luther King Jr. speak just six months before his assassination. The force of the reverend's rhetoric inspired the famed investor to push harder for civil rights.

Berkshire Hathaway's CEO and his late wife, Susan, attended a fundraising event at Grinnell College in Iowa in October 1967, Alice Schroeder wrote in "The Snowball: Warren Buffett and the Business of Life." King gave a thundering rendition of "Remaining Awake during a Revolution."

"I remember that speech that Martin Luther King gave," Buffett said in "Becoming Warren Buffett," a HBO documentary. "That was one of the most inspiring speeches I've ever heard. Took me right out of my seat."

"He talked about 'truth forever on the scaffold, long forever on the throne, but that scaffold sways the future,'" Buffett added. "Well, he was going to be dead in six months, but that scaffold did sway the future."

Another line resounded with Buffett, according to Time magazine: "It may be true that the law can't change the heart, but it can restrain the heartless."

King's words instilled in Buffett "a sense of urgency to do something more for civil rights," Schroeder wrote. His deepened resolve marked "the first time there had been space in Warren's life for anything outside of moneymaking and it was Susie's doing," Time reported.

Buffett advocated for civil rights in several ways, such as fighting against anti-Semitism. He and Susan were among the first non-Jews to join an all-Jewish country club in Omaha, and they encouraged other country clubs to admit Jews, the New York Times reported.